Protective packaging for various size and shape packages presents a common problem in the packaging industry. Packaging used in wrapping machines is typically pliable to permit proper wrapping of a package by the machine. The soft, stretchy characteristics of the packaging necessary for a good wrap tend to make cutting or severing a sheet from a continuous web difficult. Normally used are knife blades having a serrated cutting edge defining sharp cutting points which initially pierce the web to facilitate cutting or tearing of the web along the length of the cutting blade.
One design of packaging machine provides for wrapping packages, particularly articles supported on trays, by elevating the packages into stretched film sheets. The sheets are severed from a continuous web by means of a pivotally mounted, cam actuated knife blade. The knife blade includes an upwardly extending serrated cutting edge which is reciprocated through a web drawn from the continuous web source. A bracket mounted above the drawn web defines a channel into which the knife blade is inserted to sever a sheet from the continuous web.
Other cutting devices have been developed to more easily cut soft, pliable packaging materials. However, such cutters tend to be complicated, expensive or deficient in some other respect. One such improved cutting device is described in U.S. Pat. No. 4,620,467 to Margraf et al. which discloses a cutting device for packaging material using knives on each side of the web to cut the web while the web is held immobile on the upstream side.
The need exists for a further improved cutter to be used with a package wrapping machine wherein soft, pliable continuous web material is severed into sheets to be wrapped about packages by the wrapping machine. To be effective, the improved film cutter must be reliable, inexpensive and, preferably, be easily useable with existing wrapping machines to permit the use of a larger variety of materials by the machine.
Therefore, it is an object of this invention to provide a method and apparatus for segmenting a continuous web into sheets of predetermined length.
Another object of this invention is to provide an apparatus for segmenting a continuous web wherein the effectiveness of the cutting step is enhanced by web clamping means on both the upstream and downstream side of the cutting blade.
A further object of this invention is to provide a web cutting apparatus having a self-adjusting web delivery means which eliminates web jamming and enhances safety.
It is a further object of this invention to provide an apparatus and method for simply and reliably cutting soft, pliable web material of irregular thicknesses.